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//计算时间差几天．
$from=mktime(0,0,0,$month1,$day1,$year1);
$to=mktime(0,0,0,$month2,$day2,$year2);
$day_diff=($to-$from)/86400;
就是这个了你变一形就可以了．
也就是把x+y=z
变成z-x=y
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86400=246060
一天的秒数